Electrochemical energy storage device of high specific power and electrodes for said device

ABSTRACT

The claimed invention relates to electrical engineering, and in particular to production of rechargeable electrochemical energy storage devices of high specific power. Positive and negative electrodes for electrochemical energy storage device of high specific power according to the invention comprise active element interacting with aqueous alkaline electrolyte in the process of redox charge-discharge reactions made of electron-conductive electrolytic alloy having composition M (l-x-y) O x H y , where M for positive electrode is nickel or nickel-based alloy, M for negative electrode—a metal out of the group: iron, nickel, cobalt or an alloy on the basis of a metal out of this group, x is atomic fraction of absorbed oxygen in the electrolytic alloy being within the limits of 0.01≦x≦0.4, for positive electrode preferably in the limits of 0.05≦x≦0.4, y is atomic fraction of absorbed hydrogen in the electrolytic alloy being within the limits of 0.01≦y≦0.4, for negative electrode preferably in the limits of 0.05≦y≦0.4, the said electrolytic alloy functioning simultaneously as current-carrying collector and as active material. 
     Electrochemical energy storage devices of high specific power according to three embodiments of the invention comprise at least one negative and one positive electrodes submerged in aqueous alkaline electrolyte and divided by a separator—a layer of ion-conductive but non electron-conductive material. 
     Enhancement of service life owing to increase in number of recharge cycles under conditions of elimination of ecological harmful cadmium is the technical result achieved by the invention.

TECHNICAL FIELD

The claimed invention relates to electrical engineering, and inparticular to production of rechargeable electrochemical energy storagedevices (accumulators, electrochemical capacitors) of high specificpower, designed for using them in various branches of engineering, suchas automotive industry, electrical tools, communication equipment,special electrical transport (workshop battery-operated trucks, loaders,invalid wheeled vehicles), in toys etc.

BACKGROUND OF THE INVENTION

It is well known that for many technical applications it is necessary tohave rechargeable power sources of high specific power (over 0.5 kW/kg)at a rather high specific energy (over 1 kJ/kg). Widespread accumulatorsof various types have high specific energy (100 kJ/kg and higher) butthey are not able to provide high specific power, because they possesstoo high internal resistance (M. A. Fetcenco et al. In 16^(th)International seminar and exhibit on primary and secondary batteries.Mar. 1-4, 1999, Florida, USA).

Conventional capacitors (oxide-electrolytic, oxide-semiconductor andferroelectric ones) possess high specific power (10 kW/kg and higher)but low specific energy (less than 0.5 kJ/kg) (D. Evans. The 9^(th)International seminar on double layer capacitors and similar energystorage devices. Dec. 6-8, 1999, Florida, USA).

Combination of high specific power with relatively high specific energyis attained in special electrochemical energy storage devices, forexample, in electrochemical “double-layer” capacitors, where energy isaccumulated in the form of electrostatic energy of double electricallayer on the boundary between “electrode (electron conductor) andelectrolyte (ion conductor)” (N. S. Lidorenko. Reports Acad. Sci. USSR,1974, vol. 126, p. 1261), in accumulators of special design,characterized with diminished electrode thickness (M. A. Fetcenco et al.In 16^(th) International seminar and exhibit on primary and secondarybatteries. Mar. 1-4, 1999, Florida, USA), as well as in hybridelectrochemical capacitors (RU, C1, 2145132),where one electrodeaccumulates energy in the form of electrostatic charge of doubleelectrical layer, like in electrochemical double-layer capacitors, andanother one—in the form of internal energy of electrochemical reactionsproducts, like in accumulators.

Electrochemical double-layer capacitors (N. S. Lidorenko. Reports Acad.Sci. USSR, 1974, vol. 126, p. 1261) have positive and negativeelectrodes made as a rule of carbon materials with highly developedsurface accumulating energy in the form of double-layer charge. Storedspecific energy can be calculated by the formula used for any capacitor:E _(sp) ^(max) =C·U ²/2m,  (1)where E_(sp)—specific energy per mass unit,

C—capacitance of the capacitor,

U—operation voltage,

m—mass.

Maximum (peak) specific power of a capacitor is determined with thefollowing formula:P _(sp) ^(max) =U ²/4m·R _(i),  (2)where R_(i)—equivalent internal resistance of the capacitor.

From formulae (1) and (2) it follows that increase in specific energyand specific power of electrochemical double-layer capacitors (at oneand the same mass) is possible by means of increasing operation voltage,increasing specific capacitance and decreasing internal resistance.

Increase in operation voltage of electrochemical double-layer capacitorsis achieved e.g. by going over to anhydrous organic electrolytes withdecomposition voltage over 3 V. However, in this case internalresistance R_(i) grows, i.e. power decreases. Besides, anhydrouselectrolytes are expensive, often toxic, fire hazardous and explosive.

Nevertheless, electrochemical double-layer capacitors with anhydrouselectrolytes find an application, achieving in their best samples highenough characteristics: E_(sp) ^(max)≈10 J/g, P_(sp) ^(max≈)3.5 W/g andservice life more than one hundred thousand cycles of recharge. Thoughhigh cost, fire and explosion hazards are main drawbacks limitingpossibilities for use of these capacitors.

Accumulators of special design (M. A. Fetcenco et al. In 16^(th)International seminar and exhibit on primary and secondary batteries.Mar. 1-4, 1999, Florida, USA), characterized with diminished thicknessof electrodes, have very high values of specific energy (over 20 J/g),are not expensive, use non-volatile and fire safe aqueous electrolyte,but they have comparatively low power (P_(sp) ^(max)<1W/g) and limitedservice life—at most ten thousand cycles of recharge.

The stored specific energy of an accumulator can be calculated by thefollowing formula:E_(sp) ^(max)=q₀.U/m  (3)where q₀—full charge of the accumulator at discharging by very smallcurrent.

At increase in discharge current the charge decreases, accumulatorvoltage decreases both at the first moment and during discharging, atfirst slowly, then rapidly. Usually a quick voltage drop cannot betolerated at operation of an accumulator because of unfavourable effecton service life.

Specific energy E_(sp,) released by accumulator at discharge, as well asits specific power P_(sp), depend on discharge current I:E_(sp)=q(I).U_(av)(I)/m,  (4)P_(sp)=I.U_(av)(I)/m,  (5)where q(I)—charge,

U_(av)(I)—average discharge voltage.

To achieve high values of specific power P_(sp) it is necessary to havehigh ratios I/m, i.e. high current values per mass unit of theaccumulator. It is just this reason that explains design peculiarity ofhigh-power accumulator electrodes: very small thickness of bothcurrent-carrying collectors and active material.

In hybrid electrochemical capacitors (RU, C1, 2145132) one electrode(usually negative one) operates on the principle of double-layercapacitor, the other (usually positive one)—on the principle ofaccumulator, therewith aqueous solution of electrolyte is used in thecapacitors.

Change of voltage during discharging of a hybrid electrochemicalcapacitor takes place mainly due to discharging of double-layer carbonelectrode while potential of “accumulator” electrode changes relativelyweakly. Internal resistance R_(i) depends on both electrodes since redoxreactions proceed with over-voltage.

Due to the above circumstances, hybrid electrochemical capacitors havedischarge characteristic similar to that of capacitors and theirspecific energy and power are determined with formulae (1)-(2). Hybridelectrochemical capacitors occupy an intermediate position betweenelectrochemical double-layer capacitors and accumulators, they have highspecific power (P_(sp) ^(max)≈3,5 W/g) and energy (E_(sp) ^(max)≈10J/g), they are much cheaper than double-layer capacitors with organicelectrolyte, they are fire- and explosion-proof. Service life of ahybrid electrochemical capacitor is determined by the positive electrodeand, since the discharging charge is usually several times less than itsfull charge, the number of recharge cycles may be as high as 50-100thousand cycles. However, due to high price of high-quality carbonmaterial used in negative electrodes price of hybrid electrochemicalcapacitors is in general higher than that of accumulators.

Positive and negative electrodes for electrochemical energy storagedevice of high specific power are known each of which is made in theform of backing carrying on one or both sides active element interactingwith aqueous alkaline electrolyte of the electrochemical energy storagedevice in the process of redox reactions of charge/discharge (RU, C1,2121728).

The backing is made out of electron-conductive but not ion-conductivematerial that is chemically and electrochemically non-active in theworking electrolyte of the electrochemical energy storage device andfunctions in the electrode simultaneously as a carrying base and as acurrent lead to the active element.

The active element is structurally formed on the backing by means ofapplying a coating of a material of initial composition including basicmetals out of a certain group or their alloy, or an alloy of at leastone metal out of this group with one or several metals-modifiers out ofthe group: copper, lanthanum or lanthanides, molybdenum, tungsten,manganese, vanadium, titanium, tin, lead, bismuth, gallium; pore-formingmetals out of the group: aluminium, zinc, alkali and alkali-earth metalsor their combinations with further chemical and/or electrochemicaltreatment of the coating in solutions of acids, salts or alkalis. Groupof basic metals for positive electrodes: iron, nickel, cobalt, silver;for negative electrode: iron, nickel, cobalt, cadmium. As a result ofthis treatment there are formed at the same time highly-developedsurface of the coating (due to etching out of pore-forming metals) andthin oxide and/or hydroxide film of active material on the coatingsurface—the film made of mono- or polymolecular compounds on theinterphase boundary “electrode-electrolyte”. Thus, the formed activeelement constitutes a highly-porous electron-conductive layer with largetrue surface area coated with electron-nonconductive oxide and/orhydroxide film. The said film and the porous coating on which the filmis located form two functionally and structurally independent components(phases) of active element, the first phase functioning as activematerial and the second phase—as current-carrying collector. Totalcurrent supply in the electrode is carried out through the backing.

The said technical concepts are taken as a prototype for the first andsecond embodiments of the present invention.

The described design of electrodes of an electrochemical energy storagedevice in which the active material of the active element (thin oxideand/or hydroxide film) is located on the developed surface of thecurrent-carrying collector (a highly-porous layer of coating on thebacking) realizes the traditional principle of mutual arrangement of themain phases participating in current-producing reactions of electrode inthe electrochemical energy storage device, namely “electron conductor(collector)—active material (oxides, hydroxides)—electrolyte”. Due toextremely small thickness of oxide and/or hydroxide film of activematerial electrochemical reactions of charge-discharge proceed with ahigh rate which determines high operating characteristics of theelectrochemical energy storage device.

Common drawback of the known positive and negative electrodes forelectrochemical energy storage device of high specific power isinsufficient service life—at most 10,000 cycles of recharge. Besides,maximum specific characteristics of negative electrode are realized whencadmium is used as the base metal, which is an environmental hazardousmaterial.

Another electrochemical energy storage device of high specific power isknown in electrodes of which the described traditional concept of mutualarrangement of main phases involved in current producing reactions isrealized, comprising at least one negative and one positive electrodessubmerged in aqueous alkaline electrolyte and divided by a separator—alayer of an ion-conductive but not electron-conductive material. Each ofthe electrodes comprises an active element interacting withelectrolyte—electron-conductive coating applied on the backing, on thedeveloped surface of which a thin oxide and/or hydroxide active materialfilm is formed taking part in charge-discharge redox reactions of theelectrode at operation of the energy storage device. Therewith, thepositive and negative electrodes differ by their basic metals being partof coating applied on the backing. For positive electrode these aremetals of the group: iron, nickel, cobalt, silver, or their alloys, fornegative electrode—metals of the group: iron, nickel, cobalt, cadmium ortheir alloys (RU, C1, 2121728).

This technical concept is taken as a prototype for third, fourth andfifth embodiments of the present invention.

Discharge characteristic of the electrochemical energy storage device byits shape lies between discharge characteristics of a capacitor and anaccumulator, but more close to the latter (Example 5, FIG. 6). Atdischarge current I=0.5 A the electrochemical energy storage devicedischarges during about 2.5 seconds at average voltage of about 1 V,then voltage quickly drops. It means that charge q (0.5)=0.5□2.5=1.25 C,U_(av)=1 V. Calculation of electrodes and separator mass based on dataof examples 3-5 gives the following: mass of negative electrode is 60mg, mass of positive electrode is 150 mg, mass of a separatorimpregnated with electrolyte is approximately 17 mg, total mass being227 mg. Calculation made according to formulae (4), (5) leads to thefollowing values: E_(sp)=5,5 J/g, P_(sp)=2,23 W/g.

This shows that in the known electrochemical energy storage device ofhigh specific power the problem of enhancement of specific electricalcharacteristics is successfully solved at acceptable cost of the devicedue to use of electrodes of a certain design. Characteristics ofspecific energy and power achieved in the prototype are well on thelevel of the best world technology. Thus the electrochemical energystorage device taken as a prototype can compete both with double-layerand hybrid electrochemical capacitors by specific energy and powergaining in price.

Drawback of the known electrochemical energy storage device of highspecific power is insufficient service life—at most 10,000 cycles ofrecharge. Besides, maximum specific characteristics are realized in theknown electrochemical energy storage device when cadmium is used as thebase metal, which is an environmental hazardous material.

SUMMARY OF THE INVENTION

The problem being solved with the present invention is how to enhancethe service life period (increase in number of recharge cycles) andexclude the ecological harmful cadmium as structural material withoutdecreasing the specific power and energy.

Essence of the claimed invention is as follows:

In the first embodiment of the invention—in the positive electrodeintended for an electrochemical energy storage device of high specificpower which comprises active elements interacting with aqueous alkalineelectrolyte in the process of redox charge-discharge reactions—theactive element is made of an electron-conductive electrolytic alloyhaving composition M_((l-x-y))O_(x)H_(y), where M is nickel ornickel-based alloy, x is atomic fraction of absorbed oxygen in theelectrolytic alloy being within the limits of 0.01 to 0.4, y is atomicfraction of absorbed hydrogen in the electrolytic alloy being within thelimits of 0.01 to 0.4, the said electrolytic alloy functionssimultaneously as current-carrying collector and as active materialwhich is participating in the processes of redox charge-dischargereactions; atomic fraction x of absorbed oxygen in the electrolyticalloy can be preferably within the limits of 0.05 to 0.4. Theelectrolytic alloy can be obtained by means of mutual electrochemicalcathode co-deposition of a metal belonging to said M group of metals andthe oxides and/or hydroxides of the M-group. In the case when the activeelement is formed as an electrolytic deposit that is separatedmechanically, chemically or electrochemically from the conductivebacking on which it has been deposited on, then the current supply canbe carried out directly to the active element; in the case when activeelement is formed as an electrolytic deposit on one or both sides of aconductive backing which is made of material that is chemically andelectrochemically stable in the electrolyte of the electrochemicalenergy storage device, then the current supply can be carried outthrough the backing.

In the second embodiment of the invention—in the negativeelectrode—intended for an electrochemical energy storage device of highspecific power which comprises active elements interacting with aqueousalkaline electrolyte in the process of redox charge-dischargereactions—the active element is made of an electron-conductiveelectrolytic alloy having composition M_((l-x-y))O_(x)H_(y), where M isa metal of the group: iron, nickel, cobalt, or an alloy on the basis ofone of the metals of this group, x is atomic fraction of absorbed oxygenin the electrolytic alloy being within the limits of 0.01 to 0.4, y isatomic fraction of absorbed hydrogen in the electrolytic alloy beingwithin the limits of 0.01 to 0.4, the said electrolytic alloy functionssimultaneously as current-carrying collector and as active materialwhich is participating in the processes of redox charge-dischargereactions; atomic fraction y of absorbed hydrogen in the electrolyticalloy can lie preferably within the limits of 0.05 to 0.4. Theelectrolytic alloy can be obtained by means of mutual electrochemicalcathode co-deposition of a metal belonging to the said M group of metalsand the oxides and/or hydroxides of the M-group. In the case when theactive element is formed as an electrolytic deposit which is separatedmechanically, chemically or electrochemically from the conductivebacking on which it have been deposited on, then the current supply canbe carried out directly to the active element; in the case when theactive element is formed as an electrolytic deposit on one or both sidesof a conductive backing which is made of material that is chemically andelectrochemically stable in the electrolyte of the electrochemicalenergy storage device, then the current supply can be carried outthrough the backing.

In the third embodiment of the invention—an electrochemical energystorage device of high specific power comprising at least one negativeand one positive electrode which are submerged in an aqueous alkalineelectrolyte and divided by a separator—a layer of ion-conductive but nonelectron-conductive material, each of the electrodes containing anactive element interacting with the electrolyte in the process of redoxcharge-discharge reactions—the active element of each of the electrodesis made of an electron-conductive electrolytic alloy that has thecomposition M_((l-x-y))O_(x)H_(y), where M for positive electrode isnickel or nickel-based alloy, M for negative electrode is a metal out ofthe group: iron, nickel, cobalt or an alloy on the basis of one of themetals of this group, x is atomic fraction of absorbed oxygen in theelectrolytic alloy being within the limits of 0.01 to 0.4, y is atomicfraction of absorbed hydrogen in the electrolytic alloy being within thelimits of 0.01 to 0.4. The said electrolytic alloy functionssimultaneously as current-carrying collector and as the active materialparticipating in the processes of redox charge-discharge reactions. Forthe positive electrode atomic fraction x of absorbed oxygen in theelectrolytic alloy can lie preferably within the limits of 0.05 to 0.4while for the negative electrode atomic fraction y of absorbed hydrogenin the electrolytic alloy lies preferably within the limits of 0.05 to0.4.

In the fourth embodiment of the invention—an electrochemical energystorage device of high specific power comprising at least one negativeand one positive electrode which are submerged in an aqueous alkalineelectrolyte and divided by a separator—a layer of ion-conductive but nonelectron-conductive material, each of the electrodes containing activeelement interacting with the electrolyte in the process of the redoxcharge-discharge reactions—the active element of the negative electrodeis made of an electron-conductive electrolytic alloy that has thecomposition M_((l-x-y))O_(x)H_(y), where M is a metal out of the group:iron, nickel, cobalt or an alloy on the basis of one of the metals ofthis group, x is atomic fraction of absorbed oxygen in the electrolyticalloy being within the limits of 0.01 to 0.4, y is atomic fraction ofabsorbed hydrogen in the electrolytic alloy being within the limits of0.01 to 0.4. The said electrolytic alloy functions simultaneously ascurrent-carrying collector and as the active material participating inthe processes of redox charge-discharge reactions. For the negativeelectrode the atomic fraction y of absorbed hydrogen in the electrolyticalloy lies preferably within the limits of 0.05 to 0.4.

In the fifth embodiment of the invention—an electrochemical energystorage device of high specific power comprising at least one negativeand one positive electrode which are submerged in an aqueous alkalineelectrolyte and divided by a separator—a layer of ion-conductive but nonelectron-conductive material, each of the electrodes containing anactive element interacting with the electrolyte in the process of redoxcharge-discharge reactions—the active element of the positive electrodeis made of an electron-conductive electrolytic alloy that has thecomposition M_((l-x-y))O_(x)H_(y), where M is nickel or nickel-basedalloy, x is atomic fraction of absorbed oxygen in the electrolytic alloybeing within the limits of 0.01 to 0.4, y is atomic fraction of absorbedhydrogen in the electrolytic alloy being within the limits of 0.01 to0.4. The said electrolytic alloy functions simultaneously ascurrent-carrying collector and as the active material participating inthe processes of redox charge-discharge reactions. For the positiveelectrode the atomic fraction x of absorbed oxygen in the electrolyticalloy lies preferably within the limits of 0.05 to 0.4

The shared inventive concept that unites the embodiments of the presentinvention is the realization of a new principle of mutual arrangement ofthe main phases participating in the current producing reactions of theelectrodes. While in all conventional electrodes the active materiallies on the collector surface thus realizing the common principle ofmutual arrangement of phases: “electron conductor (collector)—activematerial (oxides, hydroxides)—electrolyte”, in the present invention theactive material is inside the metal collector being a part of itscrystal structure and forms with it a single phase—the phase of “activeelement”.

To the applicant's knowledge there is no technical concepts identical tothe claimed ones. It allows, according to the applicant's opinion, todraw a conclusion that the invention corresponds to the “novelty”criterion (N).

As a result of realization of the features of the invention newimportant properties of the energy storage device are achieved. The newarrangement of active material inside the metal collector brings on anumber of important consequences, which radically change the propertiesof electrodes and of energy storage devices as a whole. In particular,there is no contact resistance between the collector and the activematerial and loss of electronic contact between the collector and theparticles of active material is impossible as well as are flaking andpeeling off of the active material from the collector. All this makes itpossible to create extremely thin electrodes which is the main directionfor increasing specific power.

It is just these fundamentally new properties of electrodes that permitto accomplish, in the framework of the claimed embodiments, the set taskof enhancement of service life (increase in number of recharge cycles)without decrease (even with increase) in specific power and energy. Inparticular, absence of contact resistance “collector-active material” inthe electrodes and low resistance of active material permit to increasespecific power, impossibility of flaking and peeling off of activematerial from the collector and impossibility of loss of electroniccontact between them permit to increase substantially durability of theelectrodes at cyclic load, while combination of functions of currentcollector and of active material in electrolytic alloy makes it possibleto reduce mass of electrodes and consequently to increase specificenergy and power of the electrochemical energy storage device.

In the framework of the shared inventive concept that unites theembodiments of the present invention there is proposed a new andpractically useful application of the phenomenon of excessive hydrogenand oxygen absorption by electrolytically deposited metal, namely, thereare proposed electrodes with electrolytically deposited metal carryinginside its structure absorbed hydrogen and oxygen, and electrochemicalstorage devices with such electrodes.

The new principle arrangement of main phases participating in currentproducing reactions of electrode is characterized by absence of directcontact of oxides and/or hydroxides with the electrolyte. At firstsight, according to the common opinion, it can be evidence ofunfeasibility of the claimed concepts. However, in reality it is not so,the claimed concepts are quite feasible and industrially applicablewhich can be explained in the following way.

As is well known, on nickel-oxide positive electrode of alkalineaccumulators (nickel-cadmium, nickel-zinc, nickel-iron ones) thefollowing reaction proceeds:Ni(OH)₂+OH⁻⇄NiOOH+H₂O+e⁻,  (6)where direction from left to right is charging, from right to left isdischarging.

In this reaction (6) hydroxide-ion and electrolyte water participate,i.e. the reaction proceeds under conditions when nickel hydroxide is incontact with electrolyte It may appear that if Ni(OH)₂ molecules arearranged inside the metal phase of the active element then theproceeding of reaction (6) is impossible. However, as experience showsand as the explanatory examples given below indicate, it is not thecase, reaction (6) proceeds, and with rather high rate, even under theseconditions. In order to explaine this it is practical to re-writereaction (6) in a little different form taking into account possiblepresence of absorbed hydrogen H_(ab) in the matrix of the activeelement:

where direction from left to right is charging, from right to left isdischarging.

Combination of reactions (7) and (8) gives the reaction of internaloxidation of nickel which is related to absorption of oxygen and todecrease of absorbed hydrogen content in nickel. Reaction (8) proceedson the surface of active element in contact with the electrolyte,reaction (7)—in the volume of the active element, so that mechanism ofreactions (7)-(8) implies diffusion of absorbed hydrogen in the activeelement.

Presence of a great amount of absorbed hydrogen in electrolytic alloys(deposits) of metals and its rather high diffusion rate have beenestablished long ago (O. P. Smith. Hydrogen in metals. Chicago, USA,1948, 367 p). It has been noted that the amount of absorbed hydrogen inelectrolytic deposits of such metals as tin, copper, nickel, cobalt,iron, manganese, chromium, zinc, and in the electrolytic alloys on thebasis of these metals is several orders larger than the equilibriumsolubility of hydrogen in the same metals and alloys obtained in ametallurgical process. The reasons for this phenomenon are beingdiscussed, beginning with the very early works and up to the presenttime, and up to now they have remained unclear. Nevertheless, theavailability of hydrogen able to be absorbed by electrolyticallydeposited metals and alloys, is beyond question and creates theoreticalprerequisite for practical implementation of this phenomenon not onlyfor positive electrodes (to provide proceeding of reactions of (7)-(8)type) but also for negative electrodes where reactions of hydrogenabsorption/desorption can proceed:H₂O+e⁻⇄H_(ab)+OH⁻,  (9)where direction from left to right is charging, from right to left isdischarging.

For example, in cited above book by O. P. Smith it has been establishedthat electrolytic alloys (deposits) of iron can absorb up to 3% at. ofhydrogen, nickel—up to 0.4% at, cobalt—up to 1.6% at. It can be easilycalculated that a 30 □m thick galvanic deposit (mass 25 mg/cm²)containing 5% at. of hydrogen can accumulate a charge according toreaction (9) of about 2.5 C/cm² which exceeds by several times thespecific charge of e.g. electrode of carbon materials operating bydouble-layer mechanism (see RU, C1, 2145132).

Observations made by L. V. Volkov et al. (L. V. Volkov, S. I. Gusev, V.N. Andrushchenko. Non-ferrous metals, 1981, No. 2, pp. 28-29) that thereexists a strong correlation between content of absorbed oxygen andabsorbed hydrogen in electrolytic nickel, atomic ratio between hydrogenand oxygen being between one and two, are of fundamental importance astheoretical evidence of feasibility in realizing the claimed concepts.In the article there is no explanation of this fact but one can supposethat (M-OH)-groups being present in electrolytic deposit can somehowcoordinate nearby them one more atom of hydrogen. Regardless ofmechanism of this phenomenon, it is of great importance for practicalrealization of the claimed concepts: the more (M-OH)-groups theelectrolytic alloy (deposit) contains the more hydrogen it is able toabsorb, consequently the more charge can be accumulated both byreactions (7)-(8) and (9). It means that the more absorbed oxygen theelectrolytic deposits, e.g. nickel or nickel alloys, contain, the morethey contain absorbed hydrogen as well, and that means—the better theywould operate both as positive and negative electrodes.

The explanatory examples given below corroborate this proposition, notat all self-evident, which is a consequence of the known scientificfacts above.

It is worth noting that many works on studying the hydrogen absorptionin electrolytically deposited metals are directed towards studyingproblems for overcoming the harmful effect of “hydrogenization” causing“embrittlement” and peeling off the galvanic deposits and appearance ofunwanted entrapped gases in electrolytically obtained nickel, etc. Theworks known to public don't contain any information or recommendationson the employment of the “hydrogenization” phenomenon in the electrodesof electrochemical storage devices nor any other useful employment ofthe phenomenon.

Considering the phenomenon of excessive hydrogen and oxygen absorptionnot as a deleterious phenomenon but as a useful one it is possible todeliberately increase the content of hydrogen and oxygen by optimizingthe electric deposition process, e.g. enhancing the current densityduring electric deposition (O. P. Smith. Hydrogen in Metals. Chicago,USA, 1948, 367 p.). It would be appropriate to use for positiveelectrode electrolytic nickel or electrolytic alloy on the basis ofnickel, in which atomic fraction of absorbed oxygen x is within thelimits of 0.01≦x≦0.4, preferably within the limits of 0.05≦x≦0.4, andfor negative electrode electrolytic nickel, iron, cobalt or electrolyticalloys on the basis of these metals, in which atomic fraction ofabsorbed hydrogen y is within the limits of 0.01≦y≦0.4, preferablywithin the limits of 0.05≦y≦0.4.

The choice of material composition for positive and negative electrodesis dictated by the following considerations.

In the region of potentials where positive electrode operates only asmall group of metals (nickel, silver, noble metals) is stable inalkaline aqueous solutions. Cobalt and iron are stable to a lesserextent. Therefore, from economical point of view the most preferablematerial for active element of a positive electrode is electrolyticnickel or electrolytic alloys on its basis containing rather largenumber of (M-OH)-groups in the structure but not too large, in whichcase electrolytic deposits could be too brittle and with lowconductivity.

In the region of potentials where negative electrode operates thefollowing metals and alloys on their basis are stable in alkalineaqueous solutions: iron, nickel, cobalt, cadmium, zirconium. Bismuth andtitanium are stable at a lesser extent. Cadmium is to be excluded onecological grounds and zirconium—on economical grounds. Therefore,preferable materials for negative electrode are electrolytic iron,nickel, cobalt and electrolytic alloys on the basis of one of thesemetals, containing large enough amount of absorbed hydrogen however notso large as to obtain too brittle electrolytic deposits having too lowconductivity.

The said limits of absorbed oxygen and hydrogen content in the activeelement material of positive and negative electrode respectively havebeen determined on the basis of experimental results. In particular, theexperiments have shown that at absorbed oxygen and hydrogen contentbeyond 40% at. the electrolytic deposits lose their plasticity, becomebrittle and can crumble and peel off under cyclic loads. At oxygencontent in positive electrode and hydrogen content in negative electrodebelow 5% at. specific charges of charging/discharging of the electrodesare too small and such electrodes cannot compete with commercially knownelectrodes.

It should be particularly emphasized that the offered electrodes ofelectrolytic alloys (the first and the second embodiments of the claimedinvention) can be used in electrochemical energy storage devices eithertogether (the third embodiment of the invention) or in differentcombinations with known electrodes (the fourth and fifth embodiments ofthe invention). Thus, the negative electrode according to the secondembodiment in accordance with the fourth embodiment of the invention canbe used with a known positive electrode, e.g. with positive electrode ofprototype, and the positive electrode according to the first embodimentin accordance with the fifth embodiment of the invention can be usedwith a known negative electrode, e.g. made of a carbon material.

To the applicants' knowledge the works known to the public don't containany information about influence of characteristic features of theclaimed concept on the reached technical result. The said circumstanceallows to draw a conclusion that the claimed technical concepts conformthe criterion “inventive standard” (IS).

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter the invention will be elucidated with detailed descriptionof 15 examples of realization of the same with reference to theaccompanying drawings, in which:

In FIG. 1 there is presented a schematic diagram of a double-electrodeelectrochemical energy storage device in the variant with the claimedelectrodes on the backing.

In FIG. 2 there is presented a cyclic voltammagram of the claimedelectrode according to the eighth example in the region of potentialsfor operation of negative electrode.

In FIG. 3 there is presented a cyclic voltammagram of the claimedelectrode according to the eighth example in the region of potentialsfor operation of positive electrode.

In FIG. 4 there is presented a cyclic voltammagram of the claimedelectrode according to the ninth example in the region of potentials foroperation of positive electrode.

In FIG. 5 there are presented discharge curves for a model of theclaimed electrochemical energy storage device with electrodes producedin accordance with the sixth and tenth examples.

In FIG. 6 there is presented a dependence of discharging charge onnumber of charge/discharge cycles for a model of the claimedelectrochemical energy storage device with electrodes produced inaccordance with the sixth and tenth examples.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The claimed electrochemical energy storage device of high specific poweraccording to the third embodiment of the claimed invention in therealization variant being discussed (FIG. 1) comprises negativeelectrode 1 and positive electrode 2 manufactured according to the firstand second embodiments of the claimed invention.

Electrodes 1 and 2 are submersed in aqueous alkaline electrolyte (notshown in FIG. 1). Electrodes 1 and 2 are set apart by a separator 3—alayer of ion-conductive but non electron-conductive material. Asseparator e.g. a layer of porous polymer impregnated with electrolytecan be used.

Negative 1 and positive 2 electrodes comprise active elements 4 and 5interacting with electrolyte in the process of redox reaction ofcharging/discharging. Active elements 4 and 5 are made of a conductiveelectrolytic alloy (deposit) which simultaneously functions ascurrent-carrying collector and as active material taking part inprocesses of charging/discharging redox reactions in electrodes 1 and 2respectively.

Active element 4 of negative electrode 1 is made of anelectron-conductive electrolytic alloy (deposit) of compositionM_((l-x-y))O_(x)H_(y), where M is metal of the following group: iron,nickel, cobalt, or an alloy on the basis of one of the metals of thisgroup with content of the main component at least 40% mass., x is atomicfraction of absorbed oxygen in the electrolytic alloy being withinlimits of 0.01≦x≦0.4, y is atomic fraction of absorbed hydrogen in theelectrolytic alloy being within limits of 0.01≦x≦0.4, preferably withinlimits of 0.05≦y≦0.4. The said limits of absorbed hydrogen content arecaused by the fact that at lesser hydrogen content specific charge ofcharging/discharging is too small and does not provide competitivenessof the negative electrode while at larger content the deposit becomesbrittle and its cycling stability falls.

Active element 5 of positive electrode 2 is made of anelectron-conductive electrolytic alloy (deposit) of compositionM_((l-x-y))O_(x)H_(y). where M is nickel or a nickel-based alloy withcontent of the main component at least 40% mass., x is atomic fractionof absorbed oxygen in the electrolytic alloy being within limits of0.01≦x≦0.4, preferably within the limits of 0.05≦x≦0.4, y is atomicfraction of absorbed hydrogen in the electrolytic alloy being withinlimits of 0.01≦x≦0.4. The said limits of absorbed oxygen content arecaused by the fact that at lesser oxygen content specific charge ofcharging/discharging is too small and does not provide competitivenessof the negative electrode while at larger content the deposit becomesbrittle and its cycling stability falls.

The said electrolytic alloys (deposits) are obtained by mutualelectrochemical cathode co-deposition of metals belonging to the saidgroups M, their oxides and/or hydroxides.

In the discussed example of realization the active elements 4 and 5 ofelectrodes 1 and 2 are formed as electrolytic deposits on respectiveconductive backings 6 and 7, through which in the present design currentsupply to the active elements 4 and 5 is carried out. In order torealize their functions the backings 6 and 7 are made of a materialchemically and electrochemically stable in the working electrolyte ofthe electrochemical energy storage device.

In other variants of realization (not shown in FIG. 1) the activeelements 4 and 5 of the electrodes 1 and 2 can be formed as independentconstructive elements as electrolytic deposits mechanically, chemicallyor electrochemically separated from respective conductive backings onwhich they have been deposited. In this case the active elements 4 and 5are used without backings and current supply in electrodes 1, 2 iscarried out directly to the active elements 4 and 5.

Electrochemical energy storage device according to the fourth embodimentof the claimed invention differs from the above consideredelectrochemical energy storage device according to the third embodimentof the claimed invention by that, that as positive electrode any knownand used for such purposes positive electrode is employed provided thatit is stable in aqueous alkaline electrolyte, e.g. positive electrodemade of carbon, nickel, cobalt or silver. In particular, the positiveelectrode described in prototype can be used as a positive electrode.

Electrochemical energy storage device according to the fifth embodimentof the claimed invention differs from the electrochemical energy storagedevice according to the third embodiment of the claimed invention bythat, that as negative electrode any known and used for such purposesnegative electrode is employed provided that it is stable in aqueousalkaline electrolyte, e.g. a negative electrode made of carbon, nickel,cobalt or iron. In particular, carbon electrode used in hybrid,capacitors can be employed as negative electrode.

The electrochemical energy storage devices made in the way consideredabove (according to the third, fourth and fifth embodiments) arecharacterized with improved specific characteristics and increasedservice life which is defined by permissible number of charge/dischargecycles. Improvement of properties is caused with that a new principle ofmutual arrangement of main phases participating in current producingreactions is realized in the electrodes which differs from the prototypeand consists in that active material (oxides and/or hydroxides) isarranged within a metal collector (being a part of its crystalstructure) and forms with it a unified phase—the phase of “activeelement”.

The examples of specific executions of electrodes and electrochemicalenergy storage devices given below confirm feasibility and industrialapplicability of the claimed invention and attainment of the requiredresult.

The elucidatory examples 1 to 7 relate to negative electrodes accordingto the second embodiment of the claimed invention. Conditions ofproduction (electrolyte composition, electrolysis conditions) andproperties of negative electrodes according to examples 1 to 7 arepresented in Table 1 in the end of the description. Conditions andmethods of measurement are similar for all the elucidatory examples 1-7and presented in example 1.

EXAMPLE 1

The negative electrode is obtained by electrochemical deposition(electrodeposition) of nickel on the backing made of rolled nickel foil25 μm thick under conditions given in Table 1. The composition of theobtained electrolytic alloy (deposit)—Ni_(0.67)O_(0.13)H_(0.2)—wasdefined by gas analysis of the deposit. Specific charge of the electrodewas defined by discharge curves at galvanostatic discharge of theelectrode in 30% KOH solution. Prior to discharge the electrode was heldat the potential of minus 1.0 V against mercury oxide referenceelectrode during 5 minutes. Discharging with current density of 0.1A/cm² continued until attainment of potential of minus 0.6 V. Thedischarge curve was plotted by a high speed recorder. The specificcharge was defined by multiplying the time of discharge in seconds bythe current density 0.1 A/cm². At deposit thickness of 25 μm (mass being20 mg/cm²) specific charge of the electrode is 2.3 C/cm² or 115 C/g.This value is five times higher than corresponding value for negativeelectrode in the prototype.

EXAMPLE 2

The negative electrode is obtained as in example 1 but in a differentelectrolyte and under different conditions of electrochemical deposition(see Table 1). Composition of the obtained electrolytic sediment isNi_(0.63)O_(0.15)H_(0.22), mass is 17 mg/cm², specific charge is 165 C/gwhich is higher than in example 1.

EXAMPLE 3

The negative electrode is obtained (see Table 1) by electrodeposition ofnickel-cobalt alloy on polished titanium backing with followingmechanical separation of the deposit from the backing (galvanoplasticmethod). Cobalt chloride was added to the electrolyte. Composition ofthe obtained electrolytic deposit isNi_(0.52)Co_(0.10)O_(0.015)H_(0.23), mass is 17 mg/cm², specific chargeis 170 C/cm². The deposit separated from the backing is plastic and canbe used as an electrode without any additional collector.

EXAMPLE 4

The negative electrode is obtained (see Table 1) by electrodeposition ofnickel-iron alloy on polished titanium backing with following mechanicalseparation of the deposit from the backing. Ferrous iron sulphate wasadded to the electrolyte. Composition of the obtained electrolyticdeposit is Ni_(0.53)Fe_(0.13)O_(0.14)H_(0.20), mass is 24 mg/cm²,specific charge is 133 C/g. The electrolytic deposit separated from thebacking is strong, plastic and can be used as an electrode without anyadditional collector.

EXAMPLE 5

The negative electrode is obtained (see Table 1) by electrodeposition ofcobalt-nickel alloy on polished titanium backing with followingmechanical separation of the deposit from the backing. Composition ofthe obtained electrolytic deposit is Co_(0.54)Ni_(0.15)O_(0.13)H_(0.18),mass is 20 mg/cm², specific charge is 150 C/g. The electrolytic depositseparated from the backing is strong, plastic and can be used forforming of a cylindrical electrode, e.g. by winding on a cylindricalmandrel Ø5 mm.

EXAMPLE 6

The negative electrode is obtained (see Table 1) by electrodeposition ofnickel-iron alloy on polished titanium backing with following mechanicalseparation of the deposit from the backing. Composition of the obtainedelectrolytic deposit is Fe_(0.47)Ni_(0.16)O_(0.12)H_(0.25), mass is 31mg/cm², specific charge is 129 C/g. The deposit separated from thebacking is strong, plastic and can be used as an electrode without anyadditional collector.

EXAMPLE 7

The negative electrode is obtained (see Table 1) by electrodeposition ofnickel-palladium alloy on a backing of rolled nickel foil 25 μm thick.Composition of the obtained electrolytic deposit isNi_(0.60)Pd_(0.03)O_(0.16)H_(0.21), mass is 17 mg/cm², specific chargeis 176 C/g.

The presented examples 1 to 7 prove possibility of practical realizationof the second embodiment of the claimed invention in respect to negativeelectrodes. In these examples the content of absorbed hydrogen inelectrolytic alloys (deposits) varied between 18% and 25% at. Additionalexperiments related to determination of limits of permissible content ofabsorbed hydrogen in electrolytic alloys (deposits) used in negativeelectrodes have shown that at increase in absorbed hydrogen content upto 40% at. the charge released while discharging has increased as wellas the specific energy however the electrolytic alloy (deposit) hasbecome brittle and could only be used on a backing, e.g. on nickel foilor mesh. For electrodes obtained by galvanoplastics method in whichcurrent supply is carried out directly to the active element(electrolytic deposit) the hydrogen content must be lower, e.g. similarto hydrogen content in the above discussed examples 1 to 7. The lowerlimit for absorbed hydrogen content in electrolytic deposit for anegative electrode must not be below 1% at. because at this point thespecific charge falls down to values that make the electrode useless forpractical applications.

The following explanatory examples 8 to 10 relate to positive electrodesaccording to the first embodiment of the claimed invention. Conditionsof fabrication (electrolyte composition, electrolysis conditions) andproperties of positive electrodes according to these examples arepresented in Table 2 in the end of the description. Conditions andmethods of measurement according to these examples are similar andpresented in example 8.

EXAMPLE 8

The positive electrode is obtained by electrochemical deposition(electrodeposition) of nickel on a backing of nickel foil 25 μm thickunder conditions given in Table 2. Composition of obtained electrolyticalloy (deposit) is Ni_(0.65)O_(0.18)H_(0.17), mass is 25 mg/cm²,specific charge is 88 C/g.

Specific charge was defined by the galvanostatic discharging curve frompotential +0.52 V down to +0.1 V by current density 0.1 A/cm² in 30%aqueous KOH solution. Before discharge the electrode was held atpotential +0.52 V during 5 minutes.

In FIG. 2 there is presented a cyclic voltammagram of the electrodeaccording to the eighth example in 30% KOH solution. The electrode areais 4 cm², reference electrode is a mercury oxide electrode, sweep rateis 10 mV/s. At the charging potential minus 1.0 V the holding time was50 seconds.

In FIG. 3 there is presented a cyclic voltammagram of the same electrodebut in the potential region of positive electrode operation. Sweep rateis 10 mV/s. At the charging potential +0.52 V the holding time was 50seconds.

EXAMPLE 9

The positive electrode is obtained (see Table 2) by electrodeposition ofa nickel-cobalt alloy on a backing of nickel foil 25 μm thick.Composition of the obtained electrolytic deposit isNi_(0.55)Co_(0.1)O_(0.19)H_(0.16), mass is 25 mg/cm², specific charge is96 C/g.

In FIG. 4 there is presented a cyclic voltammagram of the electrodeaccording to the ninth example in the potential region of positiveelectrode operation. The electrode area is 4 cm², sweep rate is 10 mV/s.At the charging potential +0.55 V the holding time was 50 seconds.Comparison of voltammagrams in FIG. 3 and in FIG. 4 shows that byalloying it is possible to increase the specific charge of the positiveelectrode.

EXAMPLE 10

The positive electrode is obtained (see Table 2) by electrodeposition ofa nickel-zinc-cobalt alloy on a polished titanium backing with followingmechanical separation of the deposit from the backing (galvanoplasticmethod). Composition of the obtained electrolytic deposit isNi_(0.52)Co_(0.09)Zn_(0.02)O_(0.20)H_(0.17), mass is 36 mg/cm², specificcharge is 119 C/cm².

The presented examples 8 to 10 prove feasibility of practicalrealization of the first embodiment of the claimed invention in respectto positive electrodes. In these examples content of absorbed oxygen inelectrolytic alloys (deposits) varied from 18% to 20% at. Additionalexperiments related to determining permissible limits of absorbed oxygencontent in electrolytic alloys (deposits) used in positive electrodeshave indicated that at increase of absorbed oxygen content up to 40% at.the charge released at discharging increased as well as the specificenergy however the electrolytic alloy (deposit) lost its strength andplasticity, its conductivity decreased. At absorbed oxygen content below1% at. the specific charge falls down to values that make the electrodeuseless for practical applications.

It is of great importance to emphasize the following fact, which isreadily apparent from analyzing cyclic voltammagrams of the electrodeaccording to the eighth example (see FIGS. 2 and 3). The cyclicvoltammagrams FIGS. 2 and 3 were measured on one and the same electrode,first in the region of cathode potentials, then in the region of anodepotentials. These voltammagrams prove that one and the same electrodemade according to the first or second embodiment of the claimedinvention can operate both as negative and as positive electrode. Thissupports validity of earlier presented explanations of possiblemechanism of charging-discharging processes for positive and negativeelectrodes in accordance with reactions (7)-(8) and (9). It can also bestated that the established fact that one and the same electrode canoperate both as negative and positive electrode is the best proof infavor of the hypothesis that absorbed hydrogen and oxygen dwell inelectrolytic deposits in the form of M-OH groups, possibly in veryfine-dispersed phase. At any rate, SEM photographs of deposits atmagnification ×30,000 did not permit to distinguish any fine structureof the deposit. It should be noticed as well that though negativeelectrodes (Table 1) can operate as positive ones, it is still better tochose most suitable deposition conditions specially for obtainingpositive electrodes (Table 2).

Two waves of discharging current are readily seen in the voltammagramFIG. 2. They indicate existence of two forms of absorbed hydrogen in theactive material of the electrode. One form of weaker bonded hydrogen isabsorbed at potentials from minus 0.9 V to minus 1.0 V and desorbed atpotentials from minus 1.0 V to minus 0.75 V, the second form, morestrongly bonded, is absorbed at potentials from minus 0.8 V to minus 0.9V and is desorbed at potentials from(minus 0.75 V to minus 0.65 V. Sucha behavior correlates with conclusions made half a century ago (Yu. V.Baymakov, L. M. Yevlannikov. J. Ph. Ch., 1951, v.25, issue 4, pp.483-494) about existence of two forms of absorbed hydrogen beingreleased at vacuum annealing, one form at a temperature of 450-500° C.,the other at temperatures beyond 800° C.

The proposed negative and positive electrodes presented in examples 1 to7 (see Table 1) and in examples 8 to 10 (see Table 2) can be used in thefollowing three variants of electrochemical energy storage devices: withboth proposed electrodes—positive and negative ones which corresponds tothe third embodiment of the claimed invention; with proposed negativeelectrode and a known positive electrode, e.g. an electrode of theprototype, which corresponds to the fourth embodiment of the claimedinvention; with proposed positive electrode and a known negativeelectrode, e.g. a carbon one, which corresponds to the fifth embodimentof the claimed invention.

Models of electrochemical energy storage devices related to the firstvariant of execution are presented in examples 11-12, the second variantis presented in example 13, the third one—in example 14. Example 15 is areference example, it relates to an electrochemical energy storagedevice in which a known negative electrode of carbon material and aknown positive electrode made in accordance with the prototype are used.

The properties of electrochemical energy storage devices according toexamples 11-15 are presented in Table 3 given in the end of thedescription. Measurement conditions in examples 11-15 are similar andpresented in example 11.

EXAMPLE 11

The model of electrochemical energy storage device according to thethird embodiment of the claimed invention is assembled of the negativeelectrode described in example 6 and the positive electrode described inexample 10 divided by separator of 0.05 mm thick polypropylene paperwetted with electrolyte—30% KOH solution. The model of electrochemicalenergy storage device was charged by current of 0.4 A up to voltage of1.5 V, then held during 5 minutes at constant voltage of 1.5 V.Discharge curves were recorded at three constant values of the current0.04 A, 0.4 A and 1.6 A at temperature 20° C. Change of voltage in timewas plotted with a high-speed recorder. Discharging continued untilattainment of voltage 0.7 V. Charge of discharging was defined bymultiplying the discharge current by the discharge time while averagevoltage was defined by numerical integration of the “voltage-time”curve. Mass of the model was determined by using of scale.

Calculation of specific energy and specific power was carried out byformulae (4) and (5), results of the calculations are presented in Table3.

In FIG. 5 there are presented discharge curves of the present model ofelectrochemical energy storage device. These curves have a shapeintermediate between discharge curves of accumulators and those ofcapacitors. At small values of discharge current they are more close todischarge curves of an accumulator, at larger values—more close todischarge curves of a capacitor.

Durability test of the present model of electrochemical energy storagedevice under cyclic loads is illustrated by the curve in FIG. 6 whichrepresents how discharging charge depends on number of charge/dischargecycles. The test has shown that service life exceeds 43,000 cyclesduring which no change in discharging charge has been registered—suchwas the number of cycles during the tests up to the moment of applyingthe patent.

Charging while cycling was carried out with a current of 0.4 A untilattainment of voltage 1.5 V, then the voltage was held constant duringone minute. Discharging was carried out with a current of 0.4 A untilattainment of voltage 1.1 V (50% of total charge), then the cycle wasrepeated. Charge of discharging was determined by multiplying current(0.4 A) by discharge time in seconds. Temperature range while cyclingwas 18-20° C.

Increase in durability of electrochemical energy storage device with theproposed electrodes under cyclic loading as compared to the durabilityof prototype is quite explainable. The active elements of the claimedelectrodes present compact electrolytic deposits instead of highlyporous layers with large true surface so that all the reactions ofchemical and electrochemical dissolution proceed here with incomparablylower rate. At the same time, reactions (7), (8), (9) proceed rapidlyenough owing to high hydrogen penetrability of iron-group metals,especially of electrolytic deposits of these metals.

EXAMPLE 12

The model of electrochemical energy storage device according to thethird embodiment of the claimed invention is made in the same manner asin example 11 but with other negative and positive electrodes accordingto examples 3 and 9 respectively (see Table 3). Use of these electrodesresults in some dissimilarities in characteristics of specific energyand power of this electrochemical energy storage device as compared withthe electrochemical energy storage device in example 11 (see table 3).

EXAMPLE 13

The model of electrochemical energy storage device according to thefourth embodiment of the claimed invention is assembled with negativeelectrode made according to example 6 and with positive electrode madeas in the prototype. In comparison with the prototype the model of thiselectrochemical energy storage device has essential advantages inspecific energy and power, moreover, it does not contain ecologicallyharmful cadmium. However, the model of this electrochemical storagedevice (see Table 3) is inferior to the model of electrochemical energystorage device described in example 11 where the same negative electrodeis used but the positive electrode is made in accordance with theclaimed invention. The device in example 11 also has a smaller mass dueto the combination of current collector and active material functions inthe active element.

EXAMPLE 14

The model of electrochemical energy storage device according to thefifth embodiment of the claimed invention is assembled with negativeelectrode of 0.35 mm thick carbon fabric and positive electrodeaccording to example 10. A 4-6 μm thick nickel layer was deposited onone side of carbon fabric by method of cyclotron spraying, after thatthe carbon fabric was spot welded at nine points to 25 μm thick nickelfoil used as collector. The rest of manufacturing conditions andprocedure of measurements were as in example 11. As it is seen fromTable 3, the model of such electrochemical energy storage device issubstantially inferior to the models of electrochemical energy storagedevices presented in examples 11 and 12 where both electrodes are madeaccording to the claimed proposal, as well as to the model ofelectrochemical energy storage device presented in example 13 where thenegative electrode is made according to the claimed proposal and thepositive one is made as in the prototype. By specific power at highcurrent densities the model of such an electrochemical energy storagedevice as in example 14 is close to the model of electrochemical energystorage device as per example 13 but is inferior to the models ofelectrochemical energy storage devices as per examples 11 and 12 (seeTable 3).

EXAMPLE 15

The model of electrochemical energy storage device is assembled withboth electrodes of known types. As positive electrode an electrode wasused made as in example 13 according to the prototype while the negativeelectrode was made on the basis of carbon fabric as in example 14. Therest of manufacturing and measurement conditions were as in example 11.As it is seen from the data given in Table 3 the model of thiselectrochemical energy storage device is inferior to all the previousexamples 11 to 14 both by specific energy and by specific power.

INDUSTRIAL APPLICABILITY

As can be seen from all the above all embodiments of the claimedinvention it is scientific feasible, industrial performable and solvethe set task, namely it increases the service life (increase in numberof recharge cycles) without decreasing (and even with increasing) thespecific power and energy, furthermore the ecological harmful cadmium isexcluded from the structural materials of the device.

The possibility of industrial application of the claimed technicalconcepts is beyond any doubt because they can be realized usingconventional materials and well-known industrial equipment, so that aconclusion can be drawn that the claimed invention conform the criterion“Industrial applicability” (IA).

The claimed embodiments of the invention present a substantial practicalinterest, opening up a new, never used before, direction in designingelectrochemical energy storage devices of high specific power based onthe employment of active elements in electrodes made out ofelectron-conductive electrolytic alloys (deposits) with excessivecontent of absorbed oxygen and hydrogen providing proceeding ofcharge-discharge redox reactions, the electrolytic alloy (deposit)functioning at the same time as current-carrying collector and as activematerial.

The prospects of this direction are stipulated by the potentialities ofa substantial enhancement of the service life of electrochemical energystorage devices of high specific power and energy, by simplicity and lowcost of their realization and by absence of ecological harmful materialsin the device.

TABLE 1 Fabrication conditions of negative electrodes and theirproperties Electrolyte Current Electrolysis Coating Specific Examplecomposi-tion, Temperature density, duration, thickness, charge No. g/l °C. A/cm² min. μm C/cm² Note 1 NiSO₄-150 70 12 10 25 2, 3 Backing -NiCl₂-50 nickel foil H₃BO₃ -10 25 μm 2 NiSO₄ -50 50 10 10 20 2, 8Backing - NiCl₂-150 nickel foil H₃BO₃ -10 25 μm 3 NiSO₄-150 50 10 10 202, 9 Galvano- NiCl₂ -10 plastic from CoCl₂-10 titanium H₃BO₃ -10 backing4 NiSO₄-100 70 15 10 30 3, 2 Galvano- NiCl₂-10 plastic from FeSO₄-30titanium H₃BO₃-10 backing 5 NiSO₄-50 50 12 10 25 3, 0 Galvano- CoCl₂-150plastic from H₃BO₃-10 titanium backing 6 NiSO₄-50 70 20 10 40 4, 0Galvano- FeCl₂-100 plastic from H₃BO₃-10 titanium backing 7 NiSO₄-50 5010 10 20 3, 0 Nickel foil NiCl₂-150 backing PdCl₂-2 25 μm H₃BO₃-10

TABLE 2 Fabrication conditions of positive electrodes and theirproperties Electrolyte Current Electrolysis Coating Specific Examplecomposition, Temperature density, duration, thickness, charge No. g/l °C. A/cm² min. mcm C/cm² Note 8 NiSO₄-100 40 10 15 30 2, 2 NickelNiCl₂-30 foil H₃BO₃-10 backing 25 μm 9 NiSO₄-100 50 15 10 30 2, 4Nickel- CoCl₂-10 foil KCl-20 backing H₃BO₃-10 25 μm 10  NiSO₄-100 50 1515 45 4, 3 Galvano- CoCl₂-10 plastic ZnCl₂-20 from H₃BO₃-10 titaniumbacking

TABLE 3 Properties of energy storage models Example No.$\frac{\begin{matrix}{Negative} \\{electrode}\end{matrix}}{\begin{matrix}{Positive} \\{electrode}\end{matrix}}\quad$ Model mass, g Current, A Discharging charge, CAverage discharging voltage, V Specific energy, J/g Average specificpower, W/g 11 $\frac{\begin{matrix}{{electrode}\quad{as}\quad{per}} \\{{example}\quad 6}\end{matrix}}{\begin{matrix}{{electrode}\quad{as}\quad{per}} \\{{example}\quad 10}\end{matrix}}$ 0.32 0.04 0.4 1.6 16 12  4.4 1.2 1.1 0.85 60 41 11.7 0.151.37 4.25 12 $\frac{\begin{matrix}{{electrode}\quad{as}\quad{per}} \\{{example}\quad 3}\end{matrix}}{\begin{matrix}{{electrode}\quad{as}\quad{per}} \\{{example}\quad 9}\end{matrix}}$ 0.25 0.04 0.4 1.6  9.6  7.2  2.8 1.2 1.1 0.85 46 31.7 9.5 0.19 1.76 5.4 13 $\frac{\begin{matrix}{{electrode}\quad{as}\quad{per}} \\{{example}\quad 6}\end{matrix}}{\begin{matrix}{{electrode}\quad{as}\quad{per}} \\{prototype}\end{matrix}}$ 0.39 0.04 0.4 1.6 16 12.8  5.2 1.2 1.1 0.85 49.2 36.111.3 0.12 1.13 3.50 14 $\frac{\begin{matrix}{{{Carbon}\quad{fabric}}\quad} \\{0.35\quad{mm}}\end{matrix}}{\begin{matrix}{{Electrode}\quad{as}\quad{per}} \\{{example}\quad 10}\end{matrix}}$ 0.43 0.04 0.4 1.6  8.4  6.0  2.8 1.05 1.0 0.9 20.5 14 5.9 0.10 0.93 3.35 15 $\frac{\begin{matrix}{{{Carbon}\quad{fabric}}\quad} \\{0.35\quad{mm}}\end{matrix}}{\begin{matrix}{{Electrode}\quad{as}\quad{per}} \\{prototype}\end{matrix}}$ 0.50 0.04 0.4 1.6  8.4  6.4  4.0 1.05 1.0 0.9 17.6 12.8 7.2 0.084 0.80 2.90

1. A positive electrode for an electrochemical energy storage device ofhigh specific power comprising active element interacting with aqueousalkaline electrolyte of the electrochemical energy storage device in theprocess of redox charge-discharge reactions characterized in that theactive element is made of electron-conductive electrolytic alloy havingthe composition M_((l-x-y))O_(x)H_(y), where M is nickel or nickel-basedalloy, x is the atomic fraction of absorbed oxygen in the electrolyticalloy being within the limits of 0.01 to 0.4, y is the atomic fractionof absorbed hydrogen in the electrolytic alloy being within the limitsof 0.01 to 0.4, whereby the said electrolytic alloy simultaneouslyfulfils the functions of current-carrying collector and of activematerial participating in the processes of redox charge-dischargereactions.
 2. The electrode according to claim 1 characterized in thatthe atomic fraction x of absorbed oxygen in the electrolytic alloy ispreferably within the limits of 0.05 to 0.4.
 3. The electrode accordingto claim 1 characterized in that the electrolytic alloy is obtained byway of simultaneous electrochemical cathode co-deposition of a metalbelonging to the above mentioned M metal group and its oxides and/orhydroxides.
 4. The electrode according to claim 1 characterized in thatthe current supply is effected directly to the active element which isstructurally designed as an electrolytic deposit being mechanically,chemically or electrochemically separated from an electro-conductivebacking on which it had been deposited.
 5. The electrode according toclaim 1 characterized in that the current supply is effected to theactive element via a backing, the active element being structurallydesigned as an electrolytic deposit on one or both sides of theelectro-conductive backing made of a material chemically andelectrochemically stable in the electrolyte of the electrochemicalenergy storage device.
 6. A negative electrode for an electrochemicalenergy storage device of high specific power comprising active elementinteracting with aqueous alkaline electrolyte of the electrochemicalenergy storage device in the process of redox charge-discharge reactionscharacterized in that the active element is made of electron-conductiveelectrolytic alloy having the composition M_((l-x-y))O_(x)H_(y), where Mis a metal of the group: iron, nickel, cobalt, or an alloy on the basisof one of the metals of this group, x is the atomic fraction of absorbedoxygen in the electrolytic alloy being within the limits of 0.01 to 0.4,y is the atomic fraction of absorbed hydrogen in the electrolytic alloybeing within the limits of 0.01 to 0.4, whereby the said electrolyticalloy simultaneously fulfils the functions of current-carrying collectorand of active material participating in the processes of redoxcharge-discharge reactions.
 7. The electrode according to claim 6characterized in that the atomic fraction y of absorbed hydrogen in theelectrolytic alloy is preferably within the limits of 0.05 to 0.4. 8.The electrode according to claim 6 characterized in that theelectrolytic alloy is obtained by way of simultaneous electrochemicalcathode co-deposition of a metal belonging to the above mentioned Mmetal group and its oxides and/or hydroxides.
 9. The electrode accordingto claim 6 characterized in that the current supply is effected directlyto the active element which is structurally designed as an electrolyticdeposit being mechanically, chemically or electrochemically separatedfrom an electro-conductive backing on which it had been deposited. 10.The electrode according to claim 6 characterized in that the currentsupply is effected to the active element via a backing, the activeelement being structurally designed as an electrolytic deposit on one orboth sides of the electro-conductive backing made of a materialchemically and electrochemically stable in the electrolyte of theelectrochemical energy storage device.
 11. An electrochemical energystorage device of high specific power containing at least one negativeand one positive electrodes submerged in aqueous alkaline electrolyteand separated with a layer of ion-conductive but non electron-conductivematerial, whereby each electrode contains an active element interactingwith the electrolyte in the process of charge-discharge redox reactionscharacterized in that the active element of each electrode is made outof an electron-conductive electrolytic alloy having compositionM_((l-x-y))O_(x)H_(y), where M for positive electrode is nickel or analloy on the basis of nickel, M for negative electrode is a metal out ofthe following metal group: iron, nickel, cobalt or an alloy on the basisof one of the metals of this group, x is an atomic fraction of absorbedoxygen in the electrolytic alloy which is within the limits of 0.01 to0.4, y is an atomic fraction of absorbed hydrogen in the electrolyticalloy which is within the limits of 0.01 to 0.4, whereby the abovementioned electrolytic alloy simultaneously fulfills the functions ofcurrent-carrying collector and of active material participating in theprocesses of redox charge-discharge reactions of each of the electrodes.12. The electrochemical energy storage device according to claim 11characterized in that for the positive electrode the atomic fraction xof absorbed oxygen in the electrolytic alloy is preferably within thelimits of 0.05 to 0.4 while for the negative electrode atomic fraction yof absorbed hydrogen in the electrolytic alloy is preferably within thelimits of 0.05 to 0.4.
 13. An electrochemical energy storage device ofhigh specific power containing at least one negative and one positiveelectrodes submerged in aqueous alkaline electrolyte and separated witha layer of ion-conductive but non electron-conductive material, wherebyeach electrode contains an active element interacting with theelectrolyte in the process of charge-discharge redox reactionscharacterized in that the active element of the negative electrode ismade of an electron-conductive electrolytic alloy having compositionM_((l-x-y))O_(x)H_(y), where M is a metal out of the following group:iron, nickel, cobalt or an alloy on the basis of one of the metals ofthe said group, x is an atomic fraction of absorbed oxygen in theelectrolytic alloy which is within the limits of 0.01 to 0.4, y is anatomic fraction of absorbed hydrogen in the electrolytic alloy which iswithin the limits of 0.01 to 0.4, whereby the said electrolytic alloysimultaneously fulfils the functions of both current-carrying collectorand of active material participating in the processes of redoxcharge-discharge reactions of negative electrode.
 14. Theelectrochemical energy storage device according to claim 13characterized in that for the negative electrode atomic fraction y ofabsorbed hydrogen in the electrolytic alloy is preferably within thelimits of 0.05 to 0.4.
 15. An electrochemical energy storage device ofhigh specific power containing at least one negative and one positiveelectrodes submerged in aqueous alkaline electrolyte and separated witha layer of ion-conductive but non electron-conductive material, wherebyeach electrode contains an active element interacting with theelectrolyte in the process of charge-discharge redox reactionscharacterized in that active element of positive electrode is made of anelectron-conductive electrolytic alloy having compositionM_((l-x-y))O_(x)H_(y), where M is nickel or an alloy on the basis ofnickel, x is an atomic fraction of absorbed oxygen in the electrolyticalloy being within the limits of 0.01 to 0.4, y is atomic fraction ofabsorbed hydrogen in the electrolytic alloy being within the limits of0.01 to 0.4, whereby the said electrolytic alloy simultaneously fulfilsthe functions of both current-carrying collector and of active materialparticipating in the processes of redox charge-discharge reactions ofpositive electrode.
 16. The electrochemical energy storage deviceaccording to claim 15 characterized in that for the positive electrodethe atomic fraction x of absorbed oxygen in the electrolytic alloy ispreferably within the limits of 0.05 to 0.4.
 17. The electrode accordingto claim 5, wherein said positive electrode is obtained viaelectrodeposition of said nickel on said electro-conductive backing ofnickel foil, said nickel foil being 25 um thick under conditions definedas 100 g/l NiSO₄, 30 g/l NiCl₂, 10 g/l H₃BO₃, a temperature of 40° C., acurrent density of 10 A/cm2, an electrolysis duration of 15 minutes, acoating thickness of 30 mcm, and a specific charge of 2,2 C/cm2, therebyfacilitating an obtained electrolytic alloy composition being Ni _(0.65)O _(0.18) H _(0.17), wherein a mass thereof being 25 mg/cm2 and having aspecific charge of 88 C/g.
 18. The electrode according to claim 5,wherein said positive electode is obtained via electrodeposition of anickel-cobalt alloy on a backing of nickel foil, said nickel foil being25 um thick under conditions defined as 100 g/l NiSO₄, 10 g/l CoCl₂, 20g/l KCl, 10 g/l H₃BO₃, a temperature of 50° C., a current density of 15A/cm2, an electrolysis duration of 10 minutes, a coating thickness of 30mcm, and a specific charge of 2,4 C/cm2, thereby facilitating anobtained electrolytic composition being Ni_(0.55) Co_(0.1) O_(0.19)H_(0.6), wherein a mass thereof being 25 mg/cm2 and having a specificcharge of 96 C/g.
 19. The electrode according to claim 10, wherein saidnegative electrode is obtained via electrodeposition of a nickel-ironalloy on polished titanium backing following mechanical separation ofdeposit from said polished titanium backing, wherein ferrous ironsulphate is added to electrolyte under conditions defined as 100 g/l NiSO4, 10 g/l NiCl2, 30 g/l FeSO4, 10 g/l H3BO3, a temperature of 70° C.,a current density of 10 minutes, an electrolysis duration of 10 minutes,a coating thickness of 30 um, and a specific charge of 3,2 C/cm2,thereby facilitating an obtained electrolytic compostion being Ni_(0.53)Fe_(0.13) O_(0.14) H_(0.20), wherein a mass thereof being 24 mg/cm2 andhaving a specific charge of 133 C/g.
 20. The electrode according toclaim 10, wherein said negative electrode is obtained viaelectrodeposition of a nickel-palladium alloy on a backing of rollednickel foil, said rolled nickel foil being 25 um thick under conditionsdefined as 50 g/l NiSO₄, 150 g/l NiCl₂, 2 g/l PdCl₂, 10 g/l H₃BO₃, atemperature of 50° C., a current density of 10 A/cm2, an electrolysisduration of 10 minutes, a coating thickness of 20 um, and a specificcharge of 3,0 C/cm2, thereby facilitating an obtained electrolyticcomposition being Ni_(0.60) Pd_(0.03) O_(0.16) H_(0.21), wherein a massthereof being 17 mg/cm2 and having a specific charge of 176 C/g.